Attachment 2244 Details for Bug 2091 – Detailed Debug info.

Detailed Debug info.

New Text Document.txt (text/plain), 7.10 KB, created by Vikas K Vicky on 2013-04-15 22:40:08 AEST

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Creator: Vikas K Vicky

Created: 2013-04-15 22:40:08 AEST

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>Continuation from the Steps to reproduce the problem ==>
>===============================================================================================
>
>
>Go to the source_machine and login as test1, there were 2 scp related    
>
>processes hung after exiting from the ksh. 
>
>
># ps -ef|grep scp                                                       
>
>   test1 1245328       1   0 16:32:39      -  0:00 scp /tmp/testfile     
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>test3@target_machine:/tmp/testfile                                       
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>   test1 1638838 1245328   0 16:32:39      -  0:18 /usr/bin/ssh -x      
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>-oForwardAgent no -oPermitLocalCommand no -oClearAllForwardings yes -l   
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>test3 -- target_machine scp -t -- /tmp/testfile                          
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>   test1 4850090 3998138   0 16:42:59  pts/1  0:00 grep scp              
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>                                                                         
>===============================================================================================
>
>
>Imporatant Debug Traces ( Stack Traces for both the processes )  -
>
>
>/home/test1> dbx -a 1245328                                              
>
>Waiting to attach to process 1245328 ...                                 
>
>Successfully attached to scp.                                            
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>warning: Directory containing scp could not be determined.               
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>Apply 'use' command to initialize source path.                           
>
>                                                                         
>
>Type 'help' for help.                                                    
>
>reading symbolic information ...                                         
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>stopped in waitpid at 0xd0231600                                         
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>0xd0231600 (waitpid+0x1c0) 80410014         lwz   r2,0x14(r1)            
>
>(dbx) where                                                              
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>waitpid(??, ??, ??) at 0xd0231600     <======== its waiting here                                 
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>killchild(signo = 1), line 156 in "scp.c"                                
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>__fd_poll(??, ??, ??) at 0xd024bf94                                      
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>scp.poll(__listptr = 0x2ff21e00, __nfds = 1, __timeout = -1), line 107   
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>in "poll.h"                                                              
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>scpio(f = 0xf0611120, fd = 6, _p = 0x2000a5f8, l = 16384, c =            
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>0x2ff21ef0), line 488 in "scp.c"                                         
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>source(argc = 1, argv = 0x2000268c), line 740 in "scp.c"                 
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>toremote(targ = "/tmp/testfile", argc = 2, argv = 0x2000268c), line 581  
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>in "scp.c"                                                               
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>main(argc = 2, argv = 0x2000268c), line 439 in "scp.c"                   
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>                                                                         
>
>(dbx) proc signal                                                        
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>(1)     HUP:    0x20002318              (killchild)                      
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>(2)     INT:    0x20002318              (killchild)                      
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>(13)    PIPE:   0x2000233c              (lostconn)                       
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>(15)    TERM:   0x20002318              (killchild)                      
>
>                                                                         
>
>(dbx) p signo                                                            
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>1                                                                        
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>(dbx) p do_cmd_pid                                                       
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>1638838                                                                  
>
>(dbx)                                                                    
>
>===============================================================================================                                                                        
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>/home/test1> dbx -a 1638838                                              
>
>Waiting to attach to process 1638838 ...                                 
>
>Successfully attached to ssh.                                            
>
>warning: Directory containing ssh could not be determined.               
>
>Apply 'use' command to initialize source path.                           
>
>                                                                         
>
>Type 'help' for help.                                                    
>
>reading symbolic information ...                                         
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>stopped in __fd_select at 0xd024c78c ($t1)                               
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>0xd024c78c (__fd_select+0xcc) 80410014         lwz   r2,0x14(r1)         
>
>(dbx) where                                                              
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>__fd_select(??, ??, ??, ??, ??) at 0xd024c78c       <======== its waiting here               
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>clientloop.select(__fds = 8, __readlist = 0x2003b7d8, __writelist =      
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>0x2003d928, __exceptlist = (nil), __timeout = (nil)), line 232 in        
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>"time.h"                                                                 
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>client_wait_until_can_do_something(readsetp = 0x2ff21cf0, writesetp =    
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>0x2ff21cf4, maxfdp = 0x2ff21d0c, nallocp = 0x2ff21d28, rekeying = 0),    
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>line 584 in "clientloop.c"                                               
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>client_loop(have_pty = 0, escape_char_arg = -2, ssh2_chan_id = 0), line  
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>1429 in "clientloop.c"                                                   
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>ssh_session2(), line 1329 in "ssh.c"                                     
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>main(ac = 1, av = 0x2ff22cdc), line 884 in "ssh.c"                       
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>                                                                         
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>(dbx) proc signal                                                        
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>(1)     HUP:    SIG_IGN                                                  
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>(2)     INT:    0x2001a854              (signal_handler)                 
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>(3)    QUIT:    0x2001a854              (signal_handler)                 
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>(13)    PIPE:   SIG_IGN                                                  
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>(15)    TERM:   0x2001a854              (signal_handler)                 
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>(28)   WINCH:   0x2001a860              (window_change_handler)          
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>(dbx)                                                                    
>
>                                                                         
>
>When user test1 logout from ksh on the source_machine, the terminal      
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>disconnected and the SIGHUP signal was sent to the scp process ( pid     
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>1245328 ) and its child process ( pid 1638838 ). 
>                        
>
>From the output of the dbx subcommand "proc signal", we can see process  
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>1245328 use a signal handler killchild to handle the SIGHUP signal, and  
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>process 1638838 just ignore the SIGHUP signal, SIG_IGN. 
>                 
>
>From the output of the dbx subcommand "where", we can see process        
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>1245328, called killchild function after receiving signal SIGHUP, then   
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>sent SIGHUP to its child process 1638838, and called waitpid funciton to 
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>wait its child process 1638838 to stop. 
>                                 
>
>But, process 1638838 just ignored the SIGHUP signal and kept running in   
>
>the client_loop. That's why the 2 processes hung.

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